size=int(input("请输入棋盘的大小："))
for i in range(size):
    for j in range(size):
        if i==0 and j==0:
            print("┏",end='')
        elif i==0 and j==size-1:
            print("┓",end='')
        elif i==size-1 and j==0:
            print("┗",end='')
        elif i==size-1 and j==size-1:
            print("┛",end='')
        elif j==0:
            print("┠",end='')
        elif i==size-1:
            print("┷",end='')
        elif j==size-1:
            print("┨",end='')
        elif i==0:
            print("┯",end='')
        else:
            print("┼",end='')
    print('')